A crystalline form of (R)-4-hydroxy-2-oxo-1-pyrrolidineacetamide is disclosed. The crystalline form has a diffraction peak when a diffraction angle, 2θ, is 16.66±0.2°, 17.54±0.2°, 21±0.2°, 22.16±0.2°, or 30.96±0.2°. The crystalline form can be dissolved quickly in water with a solubility greater than or equal to 90 mg/mL, features high bioavailability, has high stability at high temperature, is suitable for preparing multiple pharmaceutical compositions, and can prepare multiple formulations, such as tablets, capsules, dripping pills, sustained-release and controlled-release formulations, and lyophilized powder for injection. The method for preparing the crystalline form is carried out under a mild condition, is easy to operate, introduces a few impurities, and features good reproducibility, an easy-to-control production process and high safety, and is suitable for industrial production.
